Synthesis and characterisation of urethane-methacrylates I

The paper describes the synthesis of urethane methacrylate resins by reaction of tolylene diisocyanate (TDI), butanol-1 (B) and 2-hydroxyethylmethacrylate (HEMA) by a two step procedure. Characterisation was done using FT-IR, FT-NMR, Mass Spectroscopy. The effect of temperature on the UV-curing behaviour was investigated by differential photocalorimetry. An activation energy of 8.4 kJ/mole was found in the temperature range of 50–100°C. Free radical polymerisation in presence of benzoyl peroxide was also investigated. The polymers were stable upto 200°C in N₂ atmosphere. A two step decomposition was observed in the temperature range of 200–500°C.

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Zusammenfassung Vorliegende Arbeit beschreibt die Synthese von Urethan-methacrylat-Harzen durch die Reaktion von Toluylendiisocyanat (TDI), Butanol-1 (B) und 2-Hydroxyethylmethacrylat (HEMA) in einem zweistufigen Herstellungsverfahren. Charakterisiert wurden die Produkte mittels FT-IR, FT-NMR und Massenspektroskopie. Anhand von Differentialfotokalorimetrie wurde der Einfluß der Temperatur auf das UV-Aushärtungsverhalten untersucht. Im Temperaturbereich 50–100°C wurde eine Aktivierungsenergie von 8.4 kJ/mol gefunden. Weiterhin wurde auch die Radikalkettenpolimerisation in Gegenwart von Benzoylperoxid untersucht. In Stickstoffatmosphäre sind die Polymere bis 200°C stabil. Im Temperaturbereich 200–500°C wurde eine zweistufige Zersetzung beobachtet.

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The Instrument system of E. I. DuPont de Nemours & Co. is acknowledged for differential photocalorimeter studies.     

Morphological,mechanical, and in vitro cytocompatibility analysis of poly(vinyl alcohol)–silica glass hybrid scaffolds reinforced with cellulose nanocrystals

Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricated using the freeze-drying method. In this study, we develop molecular-level-based hybrid scaffolds with possible bioactivity behavior by adding silica sol–gel. The results showed a highly porous structure and a significant improvement in mechanical performance (stiffness) of hybrid scaffolds with an increased content of cellulose nanocrystals followed by the addition of silica-based bioactive glass. In vitro cell study with MC3T3-E1 cells on hybrid scaffolds for 1 and 3 days revealed good cell adhesion and growth. Thus, the obtained hybrid scaffold may be a competitive candidate for bone tissue engineering applications.     

Urease inhibition and anti-leishmanial assay of substituted benzoylguanidines and their copper(II) complexes

A series of N,N',N'-trisubstituted guanidines (1-6) and their copper(II) complexes, [κ(2)(O,N)-C(6)H(5)CONHC(NHC(6)H(4)Cl)NR](2)Cu(ii) (R = iso-propyl (1a), n-butyl (2a), sec-butyl (3a), tert-butyl (4a), benzyl (5a), and para-tolyl (6a)) were synthesized and characterized using elemental analysis, FTIR and NMR spectroscopy. DFT studies were used to assess the location of the protons in the free ligands. However, calculations have shown that, in all cases, hydrogen bonding from either N-H group gives conformations that are very similar in energy. Single crystal XRD studies were used to characterize ligands 1 and 4 and the related complexes 1a and 4a. The structures reveal that these complexes are mononuclear in the solid state and that copper adopts a regular square planar geometry. In both metallic species, the N, N', N'-trisubstituted guanidine ligands chelate the Cu(II) atom using the oxygen and one nitrogen. The synthesized compounds were investigated for urease inhibition using thiourea as a standard drug. Most complexes exhibit a better activity than the respective guanidines and compound 1a was found to be the most active with IC(50) = 9.83 ± 0.07 μM (the IC(50) for thiourea is 21.0 ± 0.1 μM). The species were also screened for their anti-leishmanial activity. However, all of the compounds were devoid of any significant activity.     

Antioxidant activity of phenolic and flavonoid compounds in some medicinal plants of India

In this study, total phenolics, flavonoids and vitamin C content vis-a-vis antioxidant activities were assayed in leaves and stem bark of Azadirachta indica, Butea monosperma, Cassia fistula, Mangifera indica, Syzygium cumini and Tamarindus indica using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging method. The DPPH radical scavenging activity positively correlated with the total phenolic content in both stem bark and leaf. Superoxide radical scavenging activity increased with increasing flavonoid contents. However, the vitamin C content could not be correlated with DPPH and superoxide radical scavenging capacity.     

Studies on the constituents of the green alga <Emphasis Type="Italic">Ulva lactuca</Emphasis>

Phytochemical investigations on a marine green alga Ulva lactuca led to the isolation of two new compounds (E)-6-heptacosen-5-one (1) and (E)-6-octadecen-5-ol (2), along with four known compounds, (Z)-10-hexacosene (3), docosanoic acid (4), palmitic acid (5), and isofucosterol (6). Compounds 3 and 4 were isolated for the first time from this species. The structures of the compounds were deduced with the help of modern spectroscopic techniques.     

Gold‐Nanoparticle‐Decorated Boron Nitride Nanosheets: Structure and Optical Properties

Synergetic cooperation of individual components of the nanocomposites (NCs) is responsible for their novel properties that lead to various technological applications. A simple chemical process depicting the deposition of functionalized gold nanoparticles on the surface of boron nitride nanosheets (BNNSs) in solution is reported. The structure, chemical composition, and optical properties of nanosheets are systematically studied. The deposition of Au nanoparticles on BNNS (BNNS_Au) results in plasmonic band modulation, thus altering the optoelectronic properties of BNNSs. The intense surface plasmon absorption band of BNNS_Au is narrowed and red‐shifted relative to the absorption band of as synthesized monometallic BNNSs. The observations reflect the strong interfacial interaction between BNNS and Au nanoparticles. This approach constitutes a basis for a simple process leading to the preparation of functionalized BNNSs and their utilization as nanoscale templates for assembly and integration with other nanoscale materials for futuristic optoelectronic devices.     

Dielectric properties of Pb(Mg1/4Zn1/4Nb1/2)O11/4

Polycrystalline samples of Pb(Mg_1/4Zn_1/4Nb_1/2)O_11/4 have been synthesized by high temperature columbite precursor solid state reaction technique. Using X-ray diffraction (XRD) technique, compound formation in single phase cubic structure was observed and XRD analysis provided preliminary structural data. Detailed studies of dielectric properties of the compound reveal that this compound has high dielectric constant and diffuse phase transition in a wide range of temperatures around the Curie temperature. The charge deficiency of the compound presumably gets compensated in the high temperature columbite precursor process of sample preparation which is supported by single phasic form of the material.